Disaplying specific number of lines at a time from a file.

Disaplying specific number of lines from a file.

The command cat displays the complete contents of the file at a time, but in case you want to view a specific number of lines at a time

Here are a few methods to do it.

1. more :

This is probably the simplest way, the command more by default displays one page of contents at a time, to restrict the number of lines we need to pass the number as an option.

If we have a file by the name "test" with the contents

The best way to make your dreams come true is to wake up Modest doubt is called the beacon of the wise We're all just walking each other home Make no judgements where you have no compassion You must be the change you wish to see in the world Love is the way messengers from the mystery tell us things In order to learn the art of dying , one must know completely the art of living A poem should not mean. But be Love all, serve all, feed all If you want to be a rebel, be kind

If we want to view one line at a time then, we can run more as follows

more -1 test The best way to make your dreams come true is to wake up --More--(11%)

Each time you press enter the next line gets displayed, the blank lines are also treated as a line. You can change the "-1" to any number of your choice.

2. Here is a bash script that tries to achive the same as shown above.

The only way this script is better than more is that it is a little more interactive, in all other respects more is a better option, this is just for fun.

#!/bin/bash count=0 st_read=0 end=1 total=0 skip=0 iter=0 if [ $# -lt 1 ] then echo -e "\n INFO : Please pass a file name \n " exit fi if [ $# -gt 1 ] then echo -e "\n INFO: Please pass only one file name \n " exit fi while read line do #echo $total ((total++)) done < $1 echo "There are $total lines to be read" echo "How many lines do you want to view at a time ?" read lines if [ $lines -le 0 ] then echo -e "\n Invalid number" exit fi end_read=$lines while [ $end -eq 1 ] do let reading=0 while read line do if [ $reading -lt $skip ] then # echo "skiping" ((reading++)) continue elif [[ $reading -lt $end_read && $reading -ne $total ]] then echo -e "\n --> $line " ((reading++)) fi done < $1 ((iter++)) if [ $reading -lt $total ] then echo -e "\n continue reading y/n ? \n " read ans if [ $ans = "y" ] then let end_read="$end_read + $lines " let skip=" $iter * $lines " # echo "end_read $end_read $st_read" continue else echo -e "\n *** Displayed $reading lines***" let end=0 fi else echo -e "\n ***all lines displayed *** \n" let end=0 fi done

Let us save script lines.sh .

Give execute permission using

chmod 777 lines.sh

The script takes one filename as input and displays the count of number of lines present in it, before asking the user to enter the number of lines he/she wants to view at a time.

After displaying the number of lines user requested for it will prompt if the user wants to continue on reciving a confirmation it will display the next set of lines and so on till the end of the file.

If the user wants to stop in between he/she can say no when the scripts prompts for confirmation, on which the script will give the number of lines displayed and exit.

Here is a trial run on the same file used above.

$ ./lines.sh test There are 19 lines to be read How many lines do you want to view at a time ? 2 --> The best way to make your dreams come true is to wake up --> continue reading y/n ? y --> Modest doubt is called the beacon of the wise --> continue reading y/n ? n *** Displayed 4 lines***